1. Technical Field
The invention relates to a depletion-layer transistor, in particular to a (unipolar heterojunction depletion-layer transistor.
2. Discussion of Related Art
Unipolar heterojunction depletion-layer transistors are used as semiconductor components in high-frequency circuits, for example in circuits for applications in broadband and wireless communications, or in radar and sensor applications.
There is a need for transistors which can be operated at signal frequencies ranging from several 100 GHz up to the THz range. Transistors deployed in industrial production until now and designed for such high frequencies use silicon-based heterojunction bipolar transistors (HBTs), for example, with a base made of a silicon-germanium alloy.
US 2004/0232505 describes a depletion-layer transistor structure having a first multilayer tunnel structure disposed between an emitter electrode and a base electrode and permitting electron transport from the emitter into the base by means of resonant tunneling. A second multilayer structure, by means of which electrons which have tunneled from the emitter into the base can tunnel through to the collector, is provided between the base and collector electrodes.